Foil feeder for sealing unit of blister-packaging machine

ABSTRACT

A cover-foil strip is pressed by a sealing roller over blisters of a blister-foil strip passing over a pocket roller having an array of pockets corresponding generally to the blisters. A drive rotates the rollers to draw the strips in a transport direction. A sensor capable of detecting the blisters thereof is connected to a controller also connected to the drive for adjusting a rotation rate of the rollers in accordance with the detected positions of the blisters relative to the rollers. A pair of grippers upstream in the direction from the rollers are each engageable in a closed position with a respective edge of the blister-foil strip. A second drive connected with the grippers can shift the grippers between the closed positions and open positions and can reciprocate the grippers in the transport direction when in the closed positions for advancement of the blister-foil strip in the direction.

FIELD OF THE INVENTION

The present invention relates to a sealing unit of a blister-packaging machine. More particularly this invention concerns a system for feeding the blister foil and cover foil to the sealing unit of such a machine.

BACKGROUND OF THE INVENTION

In a standard blister-packaging operation a thermoplastic foil strip is formed with an array of blisters, then the foil is passed through a filling station with the blisters open upward so one or more objects, for instance pills, can be put in each blister. The thus filled blister foil then moves continuously through a sealing station where a cover foil that can be of plastic or metal is heat-sealed atop it so as to hermetically close in the objects. This is typically done by pinching the two foils together between a lower roller formed with an array of pockets corresponding to the blisters and an upper heated roller having a smooth cylindrical outer surface. Subsequently the laminated-together strips are cut into individual packages in the webs between the blisters, each package having one or more blisters. Such an operation takes place with continuous movement of the workpiece—the foil strips—at relatively high speed and, since it is typically is applied to valuable pharmaceutical products must be done very accurately without damaging the objects.

A principal problem is that heat is used to seal the two foils together. This heat should not be applied to the blisters, as it could deform them, or to the objects held in the blisters, because this could damage the objects. To this end the pockets in the lower sealing roller are normally somewhat larger than the blisters, and as described in German patent 10 2004 012 449 means is provided for adjusting the roller-rotation speed to keep these blisters centered in the roller pockets.

During operation of the machine the strips are heated and elongate somewhat, but this is a gradual effect so that during a normal run the above-described system works quite well. As the blisters drift one way or another in the transport direction, it is relatively simple to speed up or slow down the rollers slightly to maintain perfect synchronization.

The main problem occurs when the machine stops and starts, either at the start or end of a production run or when the run is interrupted because of a disturbance upstream or downstream. In this case, when the machine restarts, synchronization is lost so that a certain number of packages are spoiled until a steady-state operation with minor adjustments can again be reached.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide an improved foil feeder for the sealing unit of a blister-packaging machine.

Another object is the provision of such an improved foil feeder for the sealing unit of a blister-packaging machine that overcomes the above-given disadvantages, in particular that even when the feed of the blister foil and the cover foil between the pocket roller and the sealing roller is started and stopped, it is possible to ensure sufficient synchronicity between the blisters and the pockets.

SUMMARY OF THE INVENTION

An apparatus for sealing a cover-foil strip over blisters of a blister-foil strip. The apparatus has according to the invention a roller having an array of pockets corresponding generally to the blisters. The blister-foil strip passing over the roller with the blisters fitting in the pockets, a sealing roller juxtaposed with the pocket roller and pressing the cover-foil strip against the blister-foil strip on the pocket roller, first drive means for rotating the rollers and drawing the strips between the rollers in a transport direction, a sensor juxtaposed with the blister-foil strip adjacent the rollers and capable of detecting the blisters thereof, control means connected between the drive means and the sensors for adjusting a rotation rate of the rollers in accordance with the detected positions of the blisters relative to the rollers, a pair of grippers upstream in the direction from the rollers and each engageable in a closed position with a respective edge of the blister-foil strip, and second drive means connected with the grippers and with the control means for shifting the grippers between the closed positions and open positions disengaged from the respective edges and for reciprocating the grippers in the transport direction when in the closed positions for advancement of the blister-foil strip in the direction.

This design of the apparatus according to the invention has the advantage that as a result of the gripper-type feeders provided upstream from the pocket roller and sealing roller, strip advance occurs at the desired speed directly upstream from the roller pair so that, for example, even during startup of a thermoshaping machine integrated into the sealing apparatus, compensation may be made for an elongation of this blister foil caused by heating of the blister foil in the sealing apparatus, as well as by the increased tension.

Within the scope of the invention, it is very particularly preferred when a drive motor having a drive shaft is associated with the feed gripper. The drive shaft carries a main eccentric carrying a main link and a control eccentric carrying a control link. A support carries both of the grippers and is connected to the main link for reciprocation on a linear guide with respect to the feed direction of the foil by means of the main eccentric. This support can be a shaft carrying a radially projecting crank connected to the control link and serving for opening and closing the feed grippers. This design provides the necessary reversible motion of the feed gripper in a compact construction, the main eccentric generating the motion of the feed gripper parallel and antiparallel to the blister foil, and the control eccentric causing the feed grippers to open and close.

The necessary matching of the movements parallel and perpendicular to the feed direction of the blister foil are forcibly achieved by means of the common drive shaft for the main eccentric and the control eccentric. The crank on the support shaft allows the rotational direction of the reversible motions of the feed gripper to be easily adapted to the rotational direction of the drive shaft.

It is also within the scope of the invention that each feed gripper has a base body sliding on the linear guide and forming a gripping jaw, and also has an upper clamping jaw that is vertically shiftable linearly guided in the respective base body perpendicular to the plane of the blister foil. The positioning of the base body on the linear guide ensures a precise alignment of the gripping jaws relative to the blister foil, so that the gripping jaws may have sufficient travel in the feed direction of the blister foil so that inadequate linear contact is avoided. The base body also lends itself to guiding the clamping jaw, so that as a whole the clamping jaws traverse a precisely defined trajectory during a revolution of the drive shaft.

Within the scope of the invention it is particularly preferred when the spacing between the pockets on the periphery of the pocket roller and along the perimeter thereof are greater than the spacings between the blisters in the blister foil. As a result of this design, the controller corrects the position of the blisters only by further accelerating the pocket roller in its customary rotational direction. Thus, it is not necessary to reverse the rotational direction of the pocket roller, thereby avoiding the associated increase in stress on the blister foil and the necessity of providing a brake for the pocket roller.

It is also particularly preferred within the scope of the invention when the roller drive is synchronized with the gripper-type feeder for correcting the position of the blisters only when the feed grippers are closed. As a result, the position of the blisters is corrected only when the resulting increase in stress on the blister foil is localized at the region between the contact line between the sealing roller and the pocket roller, and at the gripper-type feeder.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a schematic side view of a sealing unit according to the invention;

FIG. 2 is a perspective view of the unit; and

FIG. 3 is a perspective view of details of the unit.

SPECIFIC DESCRIPTION

As seen in FIG. 1 an apparatus for sealing a blister foil 1 having filled blisters 3 by means of a cover foil 2 is used for packaging pharmaceuticals as blister packs in the manner described above. In this thermoshaping machine the blisters 3 in the blister foil 1 are made and then filled with objects in thermoshaping and filling stations upstream in a strip-travel direction 19 from the illustrated sealing apparatus. The function of the sealing apparatus according to the invention is to establish an air- and pressure-tight connection between the blister foil 1 and the cover foil 2 for protection of the objects in the blisters 3. Pressure and temperature act on the blister foil 1 and the sealing foil 2 during the sealing, thereby ensuring that the objects are not damaged during the sealing process.

To this end the apparatus according to the invention comprises a pocket roller 5 that is driven by a roller-drive motor 23 and has pockets 4 in its cylindrical outer surface for the blisters 3, and an adjacent sealing roller 6 with a cylindrical outer surface, the two rollers 5 and 6 being rotatable about respective parallel horizontal axes lying in a vertical plane perpendicular to the direction 19. The blister foil 1 and cover foil 2 are pinched between the rollers 5 and 6.

The apparatus further comprises a controller 24 connected to the motor 23 for controlling the position the pockets 3 with respect to the blisters 4 in the pocket roller 5 in which the pockets 3 fit. This is done by varying the rotation speed of the pocket roller 5 in accordance with a blister position detected by an electric-eye sensor 7 provided immediately upstream of the nip between the rollers 5 and 6. This controller 24 can vary the motor speed 24 to ensure that during a production run the blisters 3 engage centrally in the pockets 4 at a slight spacing from the flanks of the pockets 4 so that the hot roller 5 does not melt through the sides of the blisters 3 and damage the blisters 3 or their contents.

Such a controller 24 operates very well during continuous operation, i.e. during continuous movement of the blister foil 1. As a result of the variation in various parameters of the sealing process during starting and stopping the foil drive as well as the sealing apparatus, problems arise in particular when the blister foil 1 gets longer because of a rise in temperature or increased tension so that the spacings between the blisters 3 no longer correspond to the spacings between the pockets 4 on the surface of the pocket roller 5, 50 that the controller 24 must compensate for larger deviations.

To deal with this, the apparatus according to the invention includes a gripper feed device 8 upstream in the direction 19 from the rollers 5 and 6. This device 8 has two feed grippers 9 that can close to grasp respective edges of the blister foil 1 and advance the blister foil 1 at the necessary foil-travel speed. If the blister foil 1 is at room temperature with a specified tension before start-up of the apparatus according to the invention, when the foil drive 24 is started and the sealing roller 6 is heated, elongation occurs in the blister foil 1 upstream from the sealing roller 6 and the pocket roller 5. For a continuously running foil drive, elongation of the blister foil 1 upstream from the pocket roller causes it not to advance at the necessary foil speed. This is corrected by the gripper-type feeder 8 that feeds the blister foil 1 to the sealing apparatus between the sealing roller 6 and the pocket roller 5 at the required foil-travel speed.

A drive motor 25 having a drive shaft 10 powers the gripper-type feeder 8. The shaft 10 carries as also shown in FIGS. 2 and 3 a main eccentric 11 on which is mounted a main link 12 and a second eccentric on which is mounted a control link 14. A control rod 16 extending horizontally perpendicular to the direction has its ends journaled in end plates 21 of the feeder that are slidable horizontally on a linear guide 15 parallel to the feed direction 10 of the foils 1. A cam 17 is provided on each end of the control rod 16 that carries a crank 20 connected to the outer end of the control link 12 so that rotation of the shaft 10 horizontally reciprocates the plates 21 horizontally while rotating the cams 17.

Each of the cams 17 vertically engages a respective upwardly spring-biased upper gripper jaw 22. Each plate 21 forms a lower jaw cooperating with one of the upper jaws 22 and forming therewith one of the grippers 9 that can close on a respective edge of the strip 1. The eccentrics 11 and 13 and crank 20 are oriented such that, starting from an upstream end position with the upper jaws 22 raised off the lower jaws 21 in an open position, with each 360° revolution of the shaft 10 in a clockwise direction 18, first the upper jaws 22 drop down to grip the strip edges and then both grippers 9 move downstream in the direction 19 to a downstream end position where the jaws 22 are raised to release the strip 1, advancing the strip 1 at a perfectly controlled travel speed. Then the grippers 9 are moved back upstream opposite to the direction 19 to the upstream end position where the cycle can be repeated.

The drive of the roller 6 is synchronized with the gripper-type feeder 8 for correcting the position of the pockets 4 in the operating state in which the feed grippers 9 are closed. It should be further noted that the spacings between the pockets 4 on the surface of the pocket roller 1 and along the perimeter thereof are greater than the spacings between the blisters 3 in the blister foil 1, so that the position of the pocket roller 5 is corrected only when the rotational direction is identical. In practice this position correction is triggered by a brief increase in the speed of the roller drive, as needed. Because the difference in the spacing between the recesses 4 in the pocket roller 5 relative to the blisters 3 in the blister foil 1 may be selected to be very small to achieve the desired effect for synchronizing the rotational direction, this is seldom necessary. Thus, there is no excessive stress on the roller drive and the components used in the apparatus as the result of uneven operation of the roller drive. 

1. An apparatus for sealing a cover-foil strip over blisters of a blister-foil strip, the apparatus comprising: a roller having an array of pockets corresponding generally to the blisters, the blister-foil strip passing over the roller with the blisters fitting in the pockets; a sealing roller juxtaposed with the pocket roller and pressing the cover-foil strip against the blister-foil strip on the pocket roller; first drive means for rotating the rollers and drawing the strips between the rollers in a transport direction; a sensor juxtaposed with the blister-foil strip adjacent the rollers and capable of detecting the blisters thereof; control means connected between the drive means and the sensors for adjusting a rotation rate of the rollers in accordance with the detected positions of the blisters relative to the rollers; a pair of grippers upstream in the direction from the rollers and each engageable in a closed position with a respective edge of the blister-foil strip; and second drive means connected with the grippers and with the control means for shifting the grippers between the closed positions and open positions disengaged from the respective edges and for reciprocating the grippers in the transport direction when in the closed positions for advancement of the blister-foil strip in the direction.
 2. The sealing apparatus defined in claim 1 wherein the second drive means includes: a motor having a rotatable output shaft; first and second eccentrics carried on the shaft; respective first and second links carried on the eccentrics and shifted in the transport direction on rotation of the shaft; a support shiftable in the direction, connected to the first link, and carrying the grippers, whereby rotation of the output shaft shifts the support in the direction; and respective cams coupled to the second link and operatively engaged with the grippers for shifting same between the open and closed positions.
 3. The sealing apparatus defined in claim 2 wherein the support is a rotatable support shaft having ends carrying the cams, the drive means further comprising: a crank extending radially from the support shaft and connected to second link, whereby rotation of the output shaft pivots the support shaft and the cams.
 4. The sealing apparatus defined in claim 3 wherein each gripper includes a lower jaw in which a respective one of the ends of the support shaft is journaled and an upper jaw shiftable vertically relative to the lower jaw and operable by the respective cam.
 5. The sealing apparatus defined in claim 1 wherein the pockets of the pocket roller are spaced apart at a spacing that is slightly larger than a spacing between the blisters of the blister strip.
 6. The sealing apparatus defined in claim 5 wherein the pockets are larger than the blisters.
 7. The sealing apparatus defined in claim 1 wherein the control means synchronizes the roller rotation only when the grippers are in the closed position.
 8. The sealing apparatus defined in claim 1 wherein each of the grippers includes an upper jaw and a lower jaw, the apparatus further comprising a linear guide supporting one of the jaws of each of the grippers for displacement only in the transport direction. 